Classifications

• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C8/00—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
  • C23C8/06—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using gases
  • C23C8/08—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using gases only one element being applied
  • C23C8/24—Nitriding
  • C23C8/26—Nitriding of ferrous surfaces

Definitions

• the invention relates to a method for nitriding steel workpieces in an atomic nitrogen-containing gas atmosphere at temperatures above 425 ° C. and pressures above 0.2 MPa.
• nitriding layers are produced on workpieces made of steel alloys in a salt bath, by gas nitriding or by plasma nitriding. These layers improve the corrosion resistance, wear resistance and vibration resistance of the steels. They generally consist of a so-called compound layer a few micrometers thick over a nitrogen diffusion layer, which generally results from the above-mentioned processes with process times in the order of 100 hours.
• gas nitriding in particular has boomed, with the steel parts being heated in an atmosphere of nitrogen-emitting gases, preferably in an ammonia atmosphere.
• a pressure vessel with a certain amount of ammonia is charged and heated to temperatures between 425 o C and 640 o C (800-1200F) heated, an ammonia pressure of a few bars which builds up in the pressure vessel.
• Nitride layers of 20 to 40 ⁇ m are obtained within about 15 hours, depending on the amount of ammonia, the pressure and the temperature. However, this procedure has not been able to establish itself in practice.
• the gas atmosphere consists of 5 to 95% by volume of ammonia and 95 to 5% by volume of molecular nitrogen, and that the nitriding takes place at constant pressure.
• the atomic nitrogen-releasing gas is ammonia, which dissociates into hydrogen and nitrogen at higher temperatures.
• the use of pure ammonia without the addition of molecular nitrogen leads to clearly poorer connection layers. In this way, nitriding layers up to 50 ⁇ m are obtained in 4 to 5 hours.
• connection layers are almost non-porous.
• the ratio of the ⁇ '- to the ⁇ -phase can be set by the process parameters and in the best case is 100% ⁇ '-phase.
• Austenitic and high-chrome steels can be nitrided without any chemical pretreatment. This method is suitable for treating workpieces without any geometric restrictions and in any number. The number is only determined by the available oven size.
• a chamber furnace can typically be heated to temperatures up to 1200 o C at an absolute internal pressure of 0.2-10 MPa.
• the treatment parameters temperature, time, absolute pressure and partial pressure of the nitrogen-releasing gas can be set in such a way that optimal treatment conditions result for each material. Values of 500 to 900 o C have proven to be favorable as nitriding temperatures. It is also important that nitriding is carried out under constant pressure throughout the nitriding time. Pressure fluctuations impair the good properties and the reproducibility of the connection layers.
• the treatment time depends on the type of steel and the desired layer thickness.

Landscapes

• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Solid-Phase Diffusion Into Metallic Material Surfaces (AREA)

Applications Claiming Priority (2)

Publications (1)

Family

ID=6418307

Family Applications (1)

Country Status (9)

Cited By (3)

Families Citing this family (4)

Citations (3)

Family Cites Families (1)

• 1990
  • 1990-11-15 DE DE19904036381 patent/DE4036381C1/de not_active Expired - Lifetime
• 1991
  • 1991-03-16 EP EP91104103A patent/EP0485686A1/de not_active Ceased
  • 1991-03-22 YU YU50691A patent/YU47730B/sh unknown
  • 1991-04-09 PL PL28979491A patent/PL289794A1/xx unknown
  • 1991-05-03 BR BR9101780A patent/BR9101780A/pt not_active Application Discontinuation
  • 1991-11-06 CS CS913360A patent/CS336091A3/cs unknown
  • 1991-11-12 JP JP29545091A patent/JPH076053B2/ja not_active Expired - Fee Related
  • 1991-11-14 RU SU5001982 patent/RU2015197C1/ru active
  • 1991-11-14 CA CA 2055541 patent/CA2055541A1/en not_active Abandoned

Patent Citations (3)

Non-Patent Citations (4)

Also Published As

Similar Documents

Legal Events